Master lock



Feb. 17, 1970 MASTER 1.00K` Filed oct. e, 19661:*

Illu

FIG. 2.

INVENTOR. JOHN F. KLEINSCHMIDT wwf@ FIG. 3.

ATTORNEYS United States Patent O U.s. c1. 'lo-151 2 Claims ABSTRACT FTHE DISCLOSURE In a pin tumbler master lock, a cylinder comprising acylinder shell having a cylindrical bore, a rotatable plug mounted inthe bore and having a keyway formed therein, a series of pinholes formedin the bore and shell, a combination of pins positioned in the pinholesand being adapted to accept the number of individual keys to rotate theplug, a cam mounted on the plug and rotatable thereby for actuating alatch bolt, and apparatus for preventing pins from dropping out of thecylinder by restricting rotation of the plug to less than 180. A springautomatically returns the plug to normal locked position if a key shouldbe withdrawn from the keyway at other than normal locked position.

This invention relates to improvements in a master lock, and moreparticularly concerns a master lock having means for preventing pinsfrom dropping out of the cylinder.

A master lock for the main door of a large apartment building, say fouror live hundred apartments, must open upon insertion of every apartmetkey. In other words, each apartment key must fit its apartment door lockand also lit the lock at the main door of the apartment building.

If the main door lock malfunctions, then many tenants are unable toenter the apartment building because they are prevented from opening thefront door. This brings complaints from the tenants, and is a fairlycommon occurrence.

Master locks are made to accommodate a number of keys by dividing thepins into a number of master pins or wafers so that each key positionsthe master pins at the shear line of the cylinder plug so that the .plugis free to rotate. One of the causes for a malfunctioning of a masterlock is that the master pins drop out of their position in the pinholesand jam the lock mechanism or drop out of the cylinder completely. Withsome of the master pins missing, some keys will not position one or morepins at the shear line and as a result the plug is prevented fromrotating.

Accordingly, it is an object of this invention to provide a master lockwhich overcomes the problems of the prior art by preventing master pinsfrom dropping out of position and from dropping out of the cylinder.

It is another object to provide a master lock which is prevented fromrotating to a position 180 away from its normal locked position.

It is another object to provide a master lock which automaticallyreturns to normal locked position if a key should be withdrawn from theplug at another position.

Other objects and advantages of this invention, including its simplicityand economy, as Well as the ease with which it may be adapted toexisting equipment, will further become apparent hereinafter and in thedrawings, in which:

FIG. 1 is a view in side elevation of a master lock constructed inaccordance with this invention with the bolt stop plate removed in orderto show the structure of the invention more clearly;

FIG. 2 is a view in section as indicated by the lines and arrows 2 2which appear in FIG. 1;

FIG. 3 is a partial view similar to that of FIG. 2 but showing the lockin its open position with the latch bolt retracted; and

FIG. 4 is a view in section of the cylinder.

Although specific terms are used in the following description forclarity, these terms are intended to refer only to the structure shownin the drawings and are not intended to dene or limit'the scope of theinvention.

Turning now to the specific embodiment of the invention selected forillustration in the drawings, there is shown a pin tumbler master lockwhich includes a cylinder 11 having a cylinder shell 13 with acylindrical bore 15, and a cylinder face 17. Cylinder 11 is providedwith threads 19 that are threaded into a hole in lock case 21. Acylinder set screw 23 is mounted in case 21 and extends into a groove 25formed in the outer surface of cylinder shell 13 for setting shell 13against further rotation when it has been rotated into its properposition.

A rotatable plug 27 is mounted in bore 15 and has a keyway 29 formedtherein.

A series of pinholes 31 are formed in shell 13, and another series ofpinholes 33 are formed in plug 27. Pinholes 31 and 33 register with eachother when the plug is in its normal locked position. A number of pins35 are positioned in pinholes 31 and 33 and are urged downwardly by pinsprings 37 which are positioned in the head portion of pinholes 31.

When a cylinder is locked, pins 35 extend across a shear line 36 formedlbetween plug 27 and shell 13 and prevent rotation of the plug. When aproper key is placed in keyway 29, such as key 38, gulleys 39 of the keycontact and lift the pins 35 so that ends of pins 35 coincide with theshear line, thus permitting rotation of plug 27 in shell 13.

Since a number of pins 35 are positioned in each pinhole, thecombination of pins 35 is adapted to accept a number of individual keysto rotate plug 27.

yCase 21 includes a miounting face 41, an armor faceplate 43, and a boltstop plate 45. A retaining screw reinforcing plate 47 is mounted on theinner side of mounting face 41 and is threaded to receive cylinder setscrew 23, and a cam mechanism 49 is mounted on inner end 51 of key plug27.

One way in which master locks of the prior art have been caused tomalfunction is to rotate keyway 29 to a position away from the normallocked position shown in FIG. 2 so that keyway bottom 53 is positionedbelow the pins in shell pinholes 31. If the key is then withdrawn fromthe keyhole in that position, pins 35 fall from pinholes 31 into keyway29 to become lodged there and prevent rotation of plug 27. It will berealized that a key with a low cut at its end can be withdrawn from thekeyway at this 180 position, even though a key with a high cut at itsend might not be withdrawable except at the normal locked position atwhich position the withdrawal of the key pushes pins 35 upwardly intoupper pinholes 31.

If the pins 35 falling into bottom 53 of keyway 29 do not jam across theshear line but fall completely into the keyway, the subsequent insertionof a key pushes the fallen pins out of the cylinder. Because of themissing pins, some of the keys subsequently inserted do not position thepins so that their ends coincide with the shear line. Accordingly, thosekeys cannot rotate the plug 27.

Another cause of malfunctioning of conventional master locks is towithdraw a key having a low cut at the end from the key at a positionsomewhere between the normally locked position and the 180 position,leaving a number of pins in plug pinholes 33. The subsequent insertionof another key cannot push the pins into the shell pinholes 31 becausethe plug pinholes are not in register with them. Accordingly, keys withhigh cuts cannot be inserted into the keyway 29 until the plug 27 isrotated to the normal locked position.

Keys can be withdrawn from the keyway 29 at other than normal lockedposition because of wear of the key and parts of the lock mechanism. Theopen ends of bore pinholes 33 adjacent the outer surface of plug 27 aremade larger by wear so that the tumbler pins 35 do not have to be at theshear line 36 in order to open the lock, thereby permitting a loose twhereby the tumbler pins 35 in plug 27, at said other position thanlocked, have freedom of movement allowing the key to be withdrawn.

To avoid these diiiiculties, my invention provides means for preventingpins 35 from dropping out of cylinder 11, and includes means forpreventing rotation of the plug 180 from normal locked position, andmeans for automatically returning the plug 27 to normal locked positionif a key should be withdrawn from keyway 29 at other than normal lockedposition.

Referring to the drawings, cam mechanism 49 includes an operating cam 55which extends downwardly from key plug 27 and extends outwardly from theperiphery of the cylinder. Cam 55 contacts a retracting arm 57 mountedon a latch bolt 59 that is slidable in case 21 and is urged outwardly toits locked position as shown in FIG. 2 by a spring 61 mounted on boltstop plate 45.

In operation, rotation of plug 27 by a key causes rotation of cam 55which moves arm 57 to retract the latch bolt 59 from the extended orlocked position shown in FIG. 2 to the retracted or open position shownin FIG. 3. Bolt stop plate 45 limits the retracting movement of the bolt59 so that plug 27 cannot rotate 180 clockwise, viewed from the front ofthe lock.

If a key 37 should be withdrawn from keyway 29 at any position otherthan the normal locked zero-degree position, plug 27 is automaticallyreturned to that position by spring 61 which pushes latch bolt 59 to itsextended position so that retracting arm 57, which bears againstoperating cam 55, rotates cam 55 and plug 27 to normal locked position.

A boss v63 extends from each side of bolt 59 and rides in slots 65formed in case 21. The extending motion of bolt I59 is limited by theend of slots 65.

A guard 67 is provided which when retracted prevents latch bolt 59 frombeing retracted from its locked position by any force which might beexerted against the head of the latch bolt such as by a card slippedinto the crack between the door and jamb.

Cam mechanism 49 also includes a hold-open cam 6 that actuates arotatable hold-open member 71 having a catch 73 adapted to contact thearm 57 and hold it in retracted position when it is desired that thelock remain open, as during the daytime. Hold-open member 71 is rotatedin a counterclockwise direction, viewed from the front of the lock, byturning hold-open cam 69 counterclockwise with the key after pushinglatch bolt 59 by 4 hand to its retracted position. The hold-open member71 is returned to normal position by rotating operating cam S5 in theclockwise direction, again viewed from the front of the lock, so thatcam 55 pushes arm 57 against member 71 to rotate it. A stop post 75limits the counterclockwise rotation of hold-open member 71, and a stoppost 76 limits its clockwise rotation. When member 71 is in contact withpost 76, it limits the counterclockwise rotation of the plug 27 byproviding a stop for cam 69.

The master lock of the present invention prevents pins from droppingfrom the cylinder shell into the bottom of the keyway because itprevents rotation of the plug to the position away from the normallocked position.

If a key is removed from the keyway when the keyway is at a positionother than the normal locked position, the pins in pinholes 33 preventinsertion of subsequent keys having high cuts. The present inventionprevents such malfunction by automatically returning the plug to thenormal locked zero-degree position, and does so by using existing lockelements since it utilizes the latch bolt spring, rather than usingseparate or additional elements.

It is to be noted that the method of inserting a cylinder into a lock inthe present invention is different from the insertion of cylindershaving conventional cams. In the present invention, the plug and cam arerotated 180 by the key so that the cam lies within the periphery ofshell 13. Then cylinder 13 is screwed into lock case 21 to its properposition. After this, the plug and cam are rotated 180 into their properposition, wherein the cam extends beyond the circumference of thecylinder shell as shown in FIG. 2.

It is important to note that cam mechanism 49 is reversible so that itworks on locks set up for left hand and right hand operation of thedoor.

It is to be understood that the form of the invention herewith shown anddescribed is to be taken as a presently preferred embodiment. Variouschanges may be made in the shape, size and arrangement of parts. Forexample, equivalent elements may be substituted for those illustratedand described herein, parts may be reversed, and certain features of theinvention may be utilized independently of the use of other features,all without departing from the spirit or scope of the invention.

What is claimed is:

1. In a pin tumbler master lock, a cylinder with a shell and cylindricalbore, a rotatable plug mounted in the bore and having a keyway formedtherein with a bottom slot, a series of pinholes formed in the lbore andconnected to the keyway, a series of pinholes formed in the shell andconnected with the bore pinholes at normal locked position, acombination of pins positioned in the pinholes for accepting a number ofindividual keys to rotate the plug, cam means mounted on the plug androtatable therewith, said cam means including a bolt-retracting cam forretracting a latch bolt, said bolt-retracting cam being normally incontact with the latch bolt, said cam means including a hold-open camlocated on the 0pposite side of the keyway from the bolt-retracting camfor moving a hold-open member into engagement with the latch bolt tohold the latch bolt in open position, and stop means for limitingrotation of the cam means and plug to less than 180 from normal lockedposition to thereby prevent the pins from dropping out of the cylinderpinholes into the keyway bottom slot when a key is removed and laterbeing lost by being pushed longitudinally through the keyway uponinsertion of a key.

2. The device of claim 1, including means for automatically returningthe keyway to normal locked position when a key is removed from thekeyway at any other position, so that the pinholes and therefore thepins will be in normal alignment and will accept another key made forthe same master series.

(References on following page) References Cited UNITED STATES PATENTSYale et al. 70-380 X Taylor 70--380 X Taylor 70-380 X Klinzing 70-134Taylor 70-380 X Smith 70--377 X Pickop.

Arens et al 70-408 X 6 1,693,028 ll/l928 Gage 70-379 X 3,073,143 1/1963Eads 70-151 FOREIGN PATENTS 5 22,980 4/1918 Denmark.

RICHARD E. MOORE, Primary Examiner R. L. WOLFE, Assistant Examiner 10U.s. C1. X.R.

